Via What's On Netflix comes word that The Midnight Club will start shooting this month and hopefully wrap up in July. Sounds like the aim is for a 2022 debut:

Mike Flanagan is already hard at work with his next Netflix Original, The Midnight Club. With filming scheduled to begin this March, the exciting new teen-horror will have plenty of people talking in 2022.

[...]

What is the production status of The Midnight Club?

Official Production Status: Filming Scheduled (Last Updated: 04/03/2021)

Principal photography is scheduled to begin in British Columbia, Canada on March 15th, 2021. Without any delays, filming is scheduled to end on July 23rd, 2021. (Source)

They have a pretty extensive cast list there, too--but it's just cast names, not the roles they'll be playing.